A master thesis from Aalborg University
Life cycle assessment of the utilisation of excess heat in district heating systems
Author(s)
Term
4. Term
Publication year
2024
Submitted on
2024-06-06
Pages
123 pages
Abstract
The utilisation of excess heat in district heating systems has been proposed as a strategy to reduce the energy sector’s environmental impact. In Denmark, excess heat could potentially meet 35-77% of the total heat demand, yet the specific environmental impacts of excess heat usage remain underexplored. This study aims to fill this gap by investigating how the utilisation of excess heat influences the environmental impact of the district heating system in Aalborg municipality. A comprehensive literature review reveals a predominant focus on CO2 and greenhouse gas emissions, highlighting the need for broader environmental assessments and a clear definition of excess heat. This study employs a consequential life cycle assessment (LCA) to address these gaps with results contextualised through lock-in theory. An hourly LCA model is developed, incorporating hourly heat supply and demand data alongside environmental impact factors for each heat supplier. This approach reveals temporal variations in environmental impacts, emphasising the dynamic nature of the district heating system. Key findings indicate that the environmental impact of excess heat is significant and context-dependent. Allocating environmental impacts to excess heat based on its share of total energy production shows that excess heat can have both positive and negative environmental effects. The study challenges the conventional view of excess heat as burden-free, demonstrating that this perspective can obscure its true environmental impacts and hinder the development of more sustainable district heating systems. Furthermore, the environmental benefit of excess heat decreases as the environmental impact of the primary heat supply decreases, underscoring the importance of continuous environmental impact evaluations. Overall, this research provides a nuanced understanding of excess heat’s environmental impact and offers a methodology for more informed decision-making in district heating system planning. By acknowledging and evaluating the environmental impacts of excess heat, policymakers can make more strategic decisions to enhance the sustainability of district heating systems.
Keywords
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